Varying hydraulic strategies within leaves, stems and roots of coexisting desert shrubs

Abstract

Effective and continuous root‐to‐leaf hydraulic transport is crucial for plant survival and growth during drought. However, the capacity to resist hydraulic dysfunction remains understudied in leaves and roots, especially for desert shrubs. This limitation seriously constrains a comprehensive understanding of shrub hydraulic strategies for drought adaptation and impairs our ability to predict shrub future dynamics under climate change. Here, based on field experiments, hydraulic vulnerability curves, pressure‐volume curves and related functional traits were measured for leaves, stems and roots of three coexisting shrub species ( Haloxylon ammodendron , Nitraria sphaerocarpa and Calligonum mongolicum ) in a typical oasis‐desert ecotone. Stomatal responses were also integrated to provide a comprehensive evaluation. H. ammodendron and N. sphaerocarpa exhibited hydraulic vulnerability segmentation along the leaf–stem–root continuum to protect their carbon‐intensive stems, with roots serving as ‘safety valves’ that prevent water backflow into dry soil. In contrast, the hydraulic vulnerability segmentation patterns of C. mongolicum varied with drought intensity: leaves acted as ‘safety valves’ to suppress excessive transpirational water loss at the initial drought, whereas under severe drought, stems were firstly sacrificed to maintain root hydraulic function. Across all three species, the relationship between hydraulic safety and efficiency differed between organs. Stems exhibited a weak safety–efficiency trade‐off, whereas roots with greater cavitation resistance were associated with higher transport efficiency. This divergence may be associated with the contrasting local microenvironments (air vs. soil) and distinct physiological functions of stems and roots. Notably, each of the three coexisting species has evolved a divergent suite of hydraulic advantages to compensate for its limitations and ensure survival. Our results, thus, highlight the importance of analysing plant hydraulic strategies from both multi‐organ and multi‐trait perspectives, which not only promotes a more accurate understanding of shrubs' drought adaptation mechanisms, but also provides scientific insights for enhancing ecological restoration and optimizing ecohydrological models in drylands. Read the free Plain Language Summary for this article on the Journal blog.